BARC-assisted process for planar recessing or removing of variable-height layers

ABSTRACT

The present disclosure provides a method of manufacturing an integrated circuit device in some embodiments. In the method, a semiconductor substrate is processed through a series of operations to form a topographically variable surface over the semiconductor substrate. The topographically variable surface varies in height across the semiconductor substrate. A polymeric bottom anti-reflective coating (BARC) is provided over the topographically variable surface. Chemical mechanical polishing is performed to remove a first portion of the BARC, and etching effectuates a top-down recessing of the BARC.

REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.14/208,697 filed on Mar. 13, 2014, the contents of which areincorporated by reference in their entirety.

BACKGROUND

The present disclosure relates to integrated circuit (IC) devicemanufacturing processes especially replacement gate processes.

In an effort to increase device densities, many years of research havebeen devoted to reducing critical dimensions (CDs) in semiconductordevices. This research has led to a long felt need to replacetraditional gate materials with high-k dielectrics and metal gates.High-k dielectrics can provide enhanced capacitance in comparison to anequivalent thickness of silicon dioxide. Metal electrodes with suitablework functions can avoid charge carrier depletion proximate theelectrode interface with the high-k dielectric. The electrodes forP-channel and N-channel transistors generally require different metals.

Suitable metals for gate electrodes can be adversely affected byprocessing used to form source and drain regions. In particular,annealing can cause an undesirable shift in the work function ofelectrode metals. This has led to the development of various newprocesses, including replacement gate (gate-last) processes. In areplacement gate process, a dummy gate stack is formed, which is a gatestack formed using polysilicon in place of metals. After source anddrain regions are formed, the polysilicon is removed to form trencheswhich are then filled with the desired metals.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a flow chart of an integrated circuit device manufacturingprocess in accordance with some embodiments.

FIGS. 2-6 illustrate a partially manufactured integrated circuit deviceundergoing processing in accordance with some embodiments of the processillustrated by FIG. 1.

FIG. 7 is a flow chart of an integrated circuit device manufacturingprocess in accordance with some embodiments.

FIGS. 8-13 illustrate a partially manufactured integrated circuit deviceundergoing processing in accordance with some embodiments of the processillustrated by FIG. 7.

FIG. 14 is a flow chart of an integrated circuit device manufacturingprocess in accordance with some embodiments.

FIGS. 15-39 illustrate a partially manufactured integrated circuitdevice undergoing processing in accordance with some embodiments of theprocess illustrated by FIG. 14.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the disclosure.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. For example, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Optimizing integrated circuit designs to make efficient use of chiparea, minimize power requirements, and maximize speed often results indesigns featuring a mixture of transistor types including N-channel andP-channel, standard voltage and low voltage, and long channel and shortchannel. This mixture of types, and the variation in pattern densityacross the chip surface, result in variations in thickness and height invarious material layers formed over the course of integrated circuitdevice manufacturing. These variations are particularly difficult tomanage in replacement gate processes where the thicknesses of somelayers can be affected by the height or depth to which a removal processhas recessed a previously deposited layer.

The present disclosure provides processes that effect a planar recessingof a topographically variable material over a substrate surface.Topographically variable means that the material varies in height acrossthe substrate. The verb “recess” is used herein to mean to cause torecede by removing an outer or uppermost portion. Recessing does notrequire that the material be lowered past another material or indented.Planar recessing means that the material is recessed to an approximatelyplanar surface, whereby any of the material above the plane issubstantially removed and any of the material below the plane is leftsubstantially intact. In some embodiments, the removal is top-downmeaning the removal is sequential from highest over the substrate tolowest with the removal front corresponding approximately with a planedescending toward the substrate surface. In some embodiments, thematerial is removed completely. In some embodiments, the material isremoved from the surface of another material, which is a material thatis susceptible to damage or is made non-planar by chemical mechanicalpolishing (CMP). In some embodiments, the topographically variablematerial is recessed to within a target range for height. In someembodiments, the material is recessed within another material that issubstantially unaffected by the recessing process. In some embodiment, aplurality of topographically variable materials are recessedsimultaneously.

FIG. 1 provides an example process 100 in accordance with someembodiments of the present disclosure. FIGS. 2-6 illustrate an exampleintegrated circuit device 200 undergoing process 100. Process 100includes action 101, which is initial processing that producestopographically variable layers 207A and 207B as shown in FIG. 2.Process 100 includes a series of actions 110 that form a uniformlyrecessed bottom anti-reflective coating (BARC) 209 and effectuate aplanar recessing or removal of layer 207A or 207B.

As shown in FIG. 2, layers 207 (layers 207A and 207B collectively) areformed over a substrate 201, a layer 203, and a layer 205. Layer 203 isan example of a material that would be damaged by CMP or that does notplanarizes well under CMP. Layer 205 is an example of a material thatcan be left substantially unaffected by recessing processing 110 andwithin which layers 207 can be recessed. In some embodiments, substrate201 includes fins 247.

Initially, both layer 207A and layer 207B are at height 206A oversubstrate 201. In this example, the height of substrate 201 isrepresented by the line S-S′, which is at the base of fins 247. Itshould be appreciated that the height of substrate 201 is merely areference plane for defining heights and that the plane identified withthe line S-S′ is only one example of a suitable reference plane. A planethrough the tops of fins 247 could also provide a suitable referenceplane. In most embodiments, substrate 201 is a wafer. A plane throughthe center of the wafer, or on a face of the wafer at some point inprocessing, could also provide a suitable reference plane.

The surface of device 200 including layers 207 has gaps 208. In someembodiments, a layer 207 that is to be made to recess has a patterndensity that varies across substrate 201. In some embodiments, a layer207 has a pattern density that varies with height continuously or inmultiple steps between its density in the plane A-A′, which is at theinitial height 206A of layers 207, and its density in the plane B-B′,which is at the lower, target height 206B for layers 207. Variations inpattern density across substrate 201, variation in pattern density withheight, and gaps 208 are challenges to recessing a layer 207 in a planarfashion. Processes provided by the present disclosure are suited tomeeting those challenges.

Layers 207 can be any of a wide variety of materials. In someembodiments, a layer 207 is a hard mask material. In some embodiments, alayer 207 is a metal. These materials can be more difficult to recess ina planar fashion than some other materials.

Processing 110 begins with act 111, filling gaps 208 and coating layers207 with a polymeric bottom anti-reflective coating (BARC) 209 as shownin FIG. 3. In some embodiments, BARC 209 is formed by spin coatingsubstrate 201 with a solution containing monomers and initiatingpolymerization. In some embodiments, BARC 209 is formed to a thicknessin the range from 300 to 5000 Å. In some embodiments, BARC 209 fills atleast 98% of the space in gaps 208.

Processing 110 continues with act 113, baking that causes BARC 209 tocross-link. In most embodiments, baking 113 is at a temperature in therange from 100° C. to 500° C. Cross-linking strengthens BARC 209 andprepares it for CMP.

Processing 110 continues with act 115, CMP. In some embodiments, CMP 115reduces the thickness of BARC 209 by from 200 to 2000 Å. In someembodiments, CMP 115 stops in the plane D1-D1′, which is within BARC 209and above layers 207 as shown in FIG. 4. In some embodiments, CMP 115stops in the plane D2-D2′ corresponding to the top of a layer 207 of amaterial to be recessed. In some embodiments, CMP 115 stops the planeD3-D3′ corresponding to a layer 205 within which process 100 recesseslayers 207. In some embodiments, CMP 115 stops on a film having athickness in the range from 5 Å to 300 Λ.

CMP 115 provides device 200 with a highly planar upper surface 218. Assuch, it is generally desirable to lower the surface 218 by CMP 115until a practical limit is reached. In some embodiment, that limit isavoiding damage to a layer 205 past which layers 207 are to be recessed.In some embodiments, that limit is avoiding damage to an underlyinglayer 203.

In some embodiments, CMP 115 provides a high selectivity between BARC209 and a layer 207 that is being recessed. A high selectivity is in therange from 10:1 to 5000:1. High selectivity for BARC 209 in CMP 115facilitates forming a highly planar surface 218.

In some embodiments, CMP 115 uses a slurry of metal oxide particles. Insome embodiments, the slurry is a colloid. A colloid contains very smallparticles. Very small particles have a high surface to volume ratio,which facilitates chemical reaction. In some embodiments, the metaloxide is one of SiO₂, Al₂O₃, and CeO₂. In some embodiments, the metaloxide particles react with hydroxyl groups in BARC 209 in a dehydrationreaction and become bound to BARC 209 through ether linkages. Reactingand bonding in this manner increases the selectivity of CMP 115 forremoving BARC 209 and increases the polishing rate.

In some embodiments, CMP 115 uses a table rotation speed in the rangefrom 30 to 110 rpm. In some embodiments, CMP 115 uses a downward forcein the range from 0.5 to 5 psi. In some embodiments, CMP 115 uses aslurry flow rate in the range from 50 to 500 ml/min. These CMPconditions can facilitate forming a highly planar surface 218,maintaining the integrity of BARC 209 during CMP 115, and maintaining ahigh polishing rate.

Processing 110 continues with act 117, etching to recess BARC 209 to atarget height 206B as shown in FIGS. 5A and 5B. In some embodiments,etching 117 has a low selectivity between BARC 209 and a layer 207. Alow selectivity (BARC 209 versus layer 207) is in the range from 1:5 to10:1. In some embodiments, etching 117 has a very low selectivitybetween BARC 209 and a layer 207. A very low selectivity is in the rangefrom 1:2 to 2:1. In some embodiments, etching 117 recesses BARC 209 andlayers 207 to approximately the same extent, which is most desirable,and produces a structure as shown in FIG. 5A. In some embodiments,etching 117 recesses BARC 209 more than layers 207 and produces astructure as shown in FIG. 5B.

In most embodiments, etching 117 is dry etching. In some embodiments,etching 117 is plasma etching with source gases that include H₂ and N₂.In some the plasma etching is characterized in part by the absence offluorine compounds from the source gases. In some embodiments, etching117 uses a flow rate for the source gases that is in the range from 5 to1000 ml/min. In some embodiments, etching 117 is carried out at apressure in the range from 1 to 100 mTorr. In some embodiments, etching117 uses a plasma source at a power setting in the range from 200 to5000 W. In some embodiments, etching 117 uses bias power up to 500 W. Insome embodiments, etching 117 is carried out with substrate 201 at atemperature in the range from 10 to 60° C. Plasma etching usingconditions within these parameters can provide a low selectivity etchthat progresses at suitably high rate.

In some embodiments, etching 117 reduces the thickness of BARC 209 byfrom 10 to 3000 Å. In some embodiments, target height 206B correspondsto the height of a layer 203 underlying one or more of the layers 207.In some embodiments, target height 206B corresponds to recessing layers207 a distance 216 within layer 205. The combination of CMP 115 toprovide a highly planar surface 218 followed by low selectivity etching117 causes BARC 209 to be uniformly recessed to the plane B-B′. Portionsof BARC 209 significantly above the plane B-B′ are effectively removed.Portions of BARC 209 and other materials forming parts of device 200that are significantly below the plane B-B′ are left intact. In someembodiments, etching 117 also causes layers 207 to be uniformly recessedto a plane.

Processing 110 optionally continues with further processing to recesslayers 107. These options are relevant for results as shown in FIG. 5Band are identified with decision 118. In some embodiments whereadditional removal is desired, process 110 continues with act 120. Act120 is selective etching where the selectivity is for removing layers107 over BARC 209 to produce a structure as shown in FIG. 5A. Foretching 120, BARC 209 masks structures below the plane B-B′.

In some embodiments where additional removal is desired, process 110continues by repeating acts 111 through 117. In these embodiments, witheach repetition layer 207 becomes further recessed and more uniformlyrecessed. The resulting structure progresses from the form of FIG. 5Btoward the form of FIG. 5A.

In some embodiments, processing 110 continues with act 119, removingBARC 209 to produces a structure as shown in FIG. 6. Act 119 isoptional. In some embodiments, removal of BARC 209 is postponed. BARC209 can be removed by any suitable dry or wet etching process.

BARC 209 can stabilize the surface of device 200 and excludecontaminants from gaps 208 during CMP 115 and etching 117. BARC 209 canuniformly recess under etching 117 to form a mask having a planar uppersurface for etching 120. BARC 209 is a relatively hard material thatfacilitates maintaining a planar upper surface of device 200 during CMP115.

As the term is used herein, a bottom anti-reflective coating (BARC) is amaterial recognized in the IC device manufacturing industry as a BARC, ahighly cross-linking organic polymer that is functional as a BARC forphotolithography, or a highly cross-linking organic polymer that hassimilar hardness and etch susceptibilities to organic polymers known inthe industry as BARCs. In some embodiments, BARC 209 is a material knownin the industry as a bottom anti-reflective coating. In someembodiments, BARC 209 is a material sold in a form suitable for spincoating onto wafers. In some embodiments, BARC 209 is a material that isfunctional as a bottom anti-reflective coating in photolithography. Insome embodiments, BARC 209 is an organic polymer or copolymer. In someembodiments, BARC 209 is susceptible to a high degree of cross-linking.

In some embodiments, BARC 209 includes monomer units having hydroxylgroups. In some embodiments, BARC 209 includes monomer units thatundergo hydration when exposed to water at a suitable pH. Unsaturatedhydrocarbons are generally susceptible to hydration. In someembodiments, BARC 209 includes monomer units that have alkenes, alkynes,or aromatic groups. In some embodiments, BARC 209 includes ester,acrylate, or isocyanate monomers. In some embodiments, BARC 209 is anacrylate polymer or copolymer. In some embodiments, BARC 209 includes anaromatic monomer. In some embodiments, BARC 209 is a styrene polymer orcopolymer. A BARC 209 having hydroxyl groups, or capable of acquiringhydroxyl groups through a hydration reaction, can react with oxideabrasive particles in a dehydration reaction that binds BARC 209 to theabrasive particles through ether linkages during CMP 115.

In some embodiments, process 100 is a hard mask removal process. In someembodiments, the hard mask removal processes removes a hard mask used topattern gates from a dummy gate stack. FIG. 7 provides an example, whichis a process 100A in accordance with some embodiments of the presentdisclosure. FIGS. 8-13 illustrate an example integrated circuit device200A undergoing process 100A. Process 100A includes a series of acts101A that form a topographically variable hard mask 219 and a series ofacts 110A, which is an embodiment of the previously describedBARC-assisted etch back 110.

The series of acts 101A includes act 121, forming a dummy gate stack 204over a substrate 201, act 123 forming a hard mask 219 over dummy gatestack 204, and act 125, pattering hard mask 219 to provide a structureas shown in FIG. 8. Although FIGS. 8-13 show process 100A being used toform dummy gates for conventional transistors, in some embodimentsprocess 100A is used to form dummy gates for finFETs. As shown in FIG.8, dummy gate stack 204 includes a layer 217 of sacrificial material. Insome embodiments, the sacrificial material is polysilicon. In someembodiments, dummy gate stack 204 includes a high-k dielectric layer213. In some embodiments, hard mask 219 is formed with a thickness inthe range from 500 to 9000 Å. In some embodiments, hard mask 219 is oneof SiO₂, SiN, SiC, SiCN, SiON, SiOCN, or a combination thereof. In someof these embodiments, hard mask 219 is one of SiO₂, SiN, and SiCN, whichare particularly useful as hard mask materials.

The series of acts 101A continues with act 127, patterning dummy gatestack 204 to form dummy gates 229, act 129, forming spacers 215, and act131, forming source/drain regions 211 as shown in FIG. 9. In someembodiments, source/drain regions 211 are formed by ion implantation. Insome embodiments, source/drain regions 211 are raised source/drainregions formed by epitaxy.

As shown in FIG. 9, acts 127 through 131 reduce the thickness 210 ofhard mask 219. In some embodiments, acts 127 through 131 thin hard mask219 until its maximum thickness 210A is in the range from 50 to 2000 Åless than its initial thickness 210. Acts 127 through 131 also causethickness 210 of hard mask 210 to vary across substrate 201 between amaximum thickness 210A and a minimum thickness 210B. These variationsstem from variations in the channel lengths 220 of dummy gates 229 andfrom variation in the pattern density of dummy gates 229 acrosssubstrate 201. Hard mask 219 is thinner in regions 202B as compared toregions 202A because the mean channel length 220 is shorter in regions202A and because the fraction of substrate 201's area that is covered byhard mask 219 is lower in region 202B. In some embodiments, processing101A causes hard mask 219 to have a variation in the range from 50 to2000 Å between its maximum thickness 210A and its minimum thickness210B.

Process 100A continues with a series of acts 110A, which are anembodiment of BARC-assisted etch back 110 including at least acts111-117 shown in FIG. 1. In processing 110A, act 111 forms BARC 209 asshown in FIG. 10. In some embodiments of processing 110A, the thicknessof BARC 209 is in the range from 500 to 5000 Å. Processing 110A includesbaking 113. In some embodiments of processing 110A, baking 113 is bakingat a temperature in the range from 150 to 300° C.

In processing 110A, CMP 115 reduces the height of BARC 209 as shown inFIG. 11. In some embodiments of processing 110A, CMP 115 lowers theheight of BARC 209 by from 500 to 2000 Å. In some embodiments ofprocessing 110A, CMP 115 stops on hard mask 219 as shown in FIG. 11. Insome other embodiments of processing 110A, CMP 115 stops in BARC 209just above the height of hard mask 219.

In processing 110A, etching 117 further reduces the height of BARC 209.In some embodiments, etching 117 removes hard mask 219 from sacrificiallayer 217 as shown in FIG. 12. In some embodiments, hard mask 219 isremoved from sacrificial layer 217 by further processing as indicated bydecision 118 in FIG. 1. In some embodiments of processing 110A, etching117 reduces the height of BARC 209 by from 50 to 3000 Å. In someembodiments of processing 110A, etching 117 takes places with substrate201 at a temperature in the range from 20 to 40° C. In some embodimentsof processing 110A, etching 117 is characterized in part by the absenceof CF₄ from plasma source gases. Plasma etching with CF₄ can damagepolysilicon, which can be the material used for sacrificial layer 217.

Processing 110A removes hard mask 219 while preserving the height 214 ofdummy gates 229. In some embodiments, the height 214B of dummy gates 229after processing 110A is at least 90% the height 214A of dummy gates 229before processing 110A. In some embodiments, the height 214B of dummygates 229 varies by 10% or less among dummy gates 229 after processing110A.

In some embodiments, process 100 is a replacement gate process. FIG. 14provides an example of a replacement gate process 100B in accordancewith some embodiments of the present disclosure. FIGS. 15-39 illustratean example IC device 200B undergoing process 100B. In some embodiments,IC device 100B includes tri-gate or gate-all-around finFETs. Process100B begins with act 133, forming fins 247 on a semiconductor substrate201 and act 135, forming a first inter-level dielectric (ILD) layer 243as shown in FIG. 15. Semiconductor substrate 201 can be any suitabletype of substrate. In some embodiments, substrate 201 is a semiconductorwafer. In some embodiments, substrate 201 is semiconductor-on-insulator.

Fins 247 include n-channel fins 247A and 247B and p-channel fins 247Cand 247D. FIG. 15 illustrates n-channel fins 247A and 247B formed in ap-well 245A and p-channel fins 247C and 247D formed in an n-well 245B,however, fins 247 can be formed and doped in any suitable manner. Insome embodiments, fins 247 are etched from substrate 201. In someembodiments, fins 247 are replacement fins produced by epitaxial growth.In some embodiments, fins 247 are etched from doped substrate 201. Insome embodiments, fins 247 are grown with dopants. In some embodiments,fins 247 are doped after their formation. In some embodiments, fins 247have a height in the range from 100 to 1000 Å.

ILD layer 243 can be formed by any suitable process. In someembodiments, ILD layer 243 is formed by depositing dielectric over fins247, chemical mechanical polishing to the height of fins 247, thenetching to recess ILD layer 243 as shown in FIG. 15. In a replacementfin process, ILD layer 243 can form a matrix in which fins 247 aregrown, after which ILD layer 243 is recessed. ILD layer 243 can beformed of any suitable dielectric or combination of dielectric.Dielectrics that can be suitable include SiO2, silicate glasses, andlow-k dielectrics.

Process 100B continues with a series of acts 100A by which dummy gates229, spacers 215, and source/drain regions 211 are formed. In someembodiments, these acts are an embodiment of process 100A of FIG. 7.FIGS. 16A and 16B show an intermediate stage of this process followingthe formation of spacers 215.

FIG. 16B provides a perspective view of portion 232 of FIG. 16A. Withthe exception of FIG. 16B, FIGS. 15-39 are cross-sectional views along aplane 230, which is shown in FIG. 16B. Plane 230 runs perpendicular tofins 247, cuts fins 247 mid-channel, and runs along the lengths of dummygates 229. Source/drain regions 211 are formed at locations 234,identified in FIG. 16B, which are outside these views. At the conclusionof acts 100A, hard mask 219 is removed as shown in FIG. 17.

Process 100B continues with act 139, forming a contact etch stop layer(CESL) 221 and act 141, forming an additional inter-level dielectriclayer 223 as shown in FIG. 18. In some embodiments, CESL 221 is SiN. Act143 is chemical mechanical polishing to expose an upper surface 236 ofdummy gates 229 as shown in FIG. 19. Process 100B continues with act145, dummy gate removal to form trenches 212, act 147, forming aninterfacial (IL) layer (not shown), and act 149, forming a high-kdielectric layer 213 as shown in FIG. 20. It should be appreciated thatthe IL layer and high-k dielectric layer 213 can be formed with dummygate stack 204 or formed subsequently as in this example.

Process 100B continues with a series of acts 101B that formtopographically variable metal layers, including work function metallayers 237 that are to be subsequently recessed within ILD layer 223.The individual and collective thicknesses of these metals will varybetween standard voltage and low voltage transistors and betweenn-channel and p-channel transistors. In some embodiments, these variablethicknesses result from a plurality of deposition, masking, and etchingoperations as shown in this example. In some embodiments, p-channel workfunction metals 237 are deposited before n-channel work function metals237 as shown in FIGS. 21-27. In some embodiments, n-channel workfunction metals 237 are deposited before p-channel work function metals237. Some or all of these work function metals 237 can be recessed byBARC-assisted etch back 110B.

Process 101B begins with act 151, forming capping and barrier metallayers 239 and act 155, forming a first work function metal (WFM1) layer237A as shown in FIG. 21. WFM1 layer 237A lines trenches 212 and risesto the tops and above trenches 212. In some embodiments capping andbarrier metal layers 239 include a TiN capping layer. In someembodiments, capping and barrier metal layers 239 include a TaN barriermetal layer. Examples of work function metals include, withoutlimitation, Ti, TiN, TiAl, W, TaN, WN, Re, Ir, Ru, and Mo. In someembodiments, a work function metal is one of Ti, TiN, TiAl, and TaN.

Process 101B continues with act 157, forming a first gate metal mask235A as shown in FIG. 22. Mask 235A masks n-channel fins 247 and some ofthe p-channel fins 247. Act 159 is an etch process that removes WFM1layer 237A from the exposed p-channel fins 247 as shown in FIG. 23. Mask235A is then stripped.

Process 101B continues with act 161, forming a second work functionmetal (WFM2) layer 237B as shown in FIG. 24. Act 163 then forms a secondgate metal mask 235B that covers n-channel fins 247 as shown in FIG. 25.Act 165 is an etch process that removes WFM2 layer 237B from thep-channel fins 247 as shown in FIG. 26. Etch process 165 is a selectiveetch that removes exposed portions of WFM2 layer 237B while leaving atleast some thickness of the exposed portions of WFM1 layer 237A intact.Mask 235B is then stripped.

Process 101B continues with act 167, forming a third work function metal(WFM3) layer 237C as shown in FIG. 27. To avoid current leaks, WFMlayers 237 are to be removed from over ILD layer 223 and recessed froman upper surface 228 of ILD layer 223. The overall thickness of WFMlayers 237 varies across substrate 201. In some embodiments, thedifference between the minimum and the maximum thickness of WFM layers237 is in the range from 100 to 500 Å. This variation in thickness andthe variation in pattern density of WFM layers 237 across substrate 201are challenges to performing a planar recessing process. In process100B, those challenges are met by applying BARC-assisted etch back 110B,which is an embodiment of BARC-assisted etch back 110 of FIG. 1.

Processing 110B begins with act 111, forming a coating of BARC 209 asshown in FIG. 28 and act 114, baking. In some embodiments of processing110B, the coating thickness of BARC 209 is in the range from 300 to 3000Å. In some embodiments of processing 110B, baking 114 is baking at atemperature in the range from 150 to 250° C.

In processing 110B, act 115, CMP, reduces the height of BARC 209 asshown in FIG. 29. In some embodiments of processing 110B, CMP 115 lowersthe height of BARC 209 by an amount in the range from 500 to 2000 Å. Insome embodiments of processing 110B, CMP 115 stops on WFM layers 237 asshown in FIG. 29. In some embodiments of processing 110B, CMP 115 stopsin BARC 209 just above the height of WFM layers 237. In some embodimentsof processing 110B, CMP 115 stops on CESL 221 or spacers 215. In someembodiments of processing 110B, CMP 115 stops on ILD layer 223.

In processing 110B, act 117, etching back, further reduces the height ofBARC 209 and recesses BARC 209 within ILD layer 223. In someembodiments, etching 117 also recesses one or more of WFM layers 237 asshown in FIG. 30. In some embodiments, etching 117 also recesses cappingand barrier metal layers 239. In some embodiments of processing 110B,one or more of WFM layers 237 are recessed by further processing asindicated by decision 118 in FIG. 1. In some embodiments of processing110B, etching 117 reduces the height of BARC 209 and WFM layers 237 byan amount in the range from 10 to 1000 Å. In some embodiments ofprocessing 110B, etching 117 takes places with substrate 201 at atemperature in the range from 20 to 40° C. In some embodiments ofprocessing 110B, etching 117 is characterized in part by the absence ofCF₄ from plasma source gases. CF₄ present during plasma etching 117 canreact with metals in WFM layers 237 to produce byproducts that act as anetch stop layer and interfere with recessing of WFM layers 237.

In some embodiments, BARC 209 is stripped at the conclusion ofprocessing 110B. In some other embodiments, as shown by this example,BARC 209 is further used to assist in forming a mask for an additionalwork function metal etch. In some alternative embodiments, thisadditional work function metal etch is carried out in a BARC-assistedetch back 110B that includes selective etch 120.

In FIG. 14, BARC-assisted etch back 110B is followed by act 171, whichis forming a third gate mask 235C as shown in FIG. 31. Mask 235C masksp-channel fins 247 and some of the n-channel fins 247. Act 173 is anetch process that removes BARC 209 from the exposed n-channel fins 247as shown in FIG. 32A. In some embodiments, act 173 is followedimmediately by act 175, which an etch process that removes WFM layers237 from the exposed n-channel fins 247 as shown in FIG. 33.

In some alternate embodiments, mask 235C is stripped before act 175 asshown in FIG. 32B. Moreover, acts 171 and 173 can occur after etching117 within processing 110B. Then, act 175, the etch process that removesWFM layers 237 from the exposed n-channel fins 247, can also be aselective etch 120 that recesses WFM layers 237. In these embodiments,BARC 209 masks WFM layers 237 below the target removal height everywherebut locations where it is desirable to remove WFM layers 237 entirely.In these alternate embodiments, the etch 175 that removes WFM layers 237from the exposed n-channel fins 247 is combined with an etch 120 thatrecesses WFM layers 237, thereby reducing the required number of etchoperations. In other embodiments mask 235C is stripped after act 175.

Process 100B continues with act 177, removing the remaining portion ofBARC to produce a structure as shown in FIG. 34, then act 179,depositing a metal 227 that fills trenches 212 as shown in FIG. 35.Metal 227 can be any suitable metal. Examples of metals that can besuitable include Al, W, Co, Cu, and Ni. Act 181 is a CMP process thatlowers metal 227 to the height of ILD layer 223 as shown in FIG. 36. Act183 is an etch process that recesses metal 227 within ILD layer 223 asshown in FIG. 37. In some embodiments, one or more of WFM metals 237 isrecessed together with metal 227 in act 183. In some embodiments,capping and barrier metal layers 239 are recessed together with metal227 in act 183. However, in some embodiments one or more of WFM metals237 and capping and barrier metal layers 239 cannot be recessedeffectively together with metal 227 in act 183. In these embodiments, atleast the layers that cannot be recessed effectively together with metal227 in act 183 are recessed by processing BARC-assisted etch back 110B.

Process 100B continues with act 185 deposits a third ILD layer 225 asshown in FIG. 36. Act 187 is a CMP process that lowers ILD layer 225 tothe same height as ILD layer 223 as shown in FIG. 39. As shown in FIG.39, the thickness 238 of ILD layer 223 is generally determined by theextent to which metal 227 is recessed by etching 183. In someembodiments, thickness 238 is in the range from 10 to 1000 Å. In someembodiments, thickness 238 is in the range from 50% to 95% the height244 of ILD layer 223 over WFM layers 237 where they lie mid-channel overfins 247. Making thickness 238 over half the height 244 provides adesirable amount of insulation, but the process window is relativelynarrow.

In some embodiments, BARC-assisted etch back 110B recesses one or moreWFM layers 237 to an equal or greater extent than etching 183 recessesmetal 227. This results in WFM layers 237 being below the upper surfaceof metal 227. In most embodiments, BARC-assisted etch back 110B does notreduce the thickness 240 of any of WFM layers 237 where they liemid-channel over fins 247. BARC-assisted etch back 110B can recess WFMlayers 237 to within the limits of these parameters.

The present disclosure provides a method of manufacturing an integratedcircuit device in some embodiments. In the method, a semiconductorsubstrate is processed through a series of operations to form atopographically variable surface over the semiconductor substrate. Thetopographically variable surface varies in height across thesemiconductor substrate. A polymeric bottom anti-reflective coating(BARC) is provided over the topographically variable surface. Chemicalmechanical polishing is performed to remove a first portion of the BARC,and etching effectuates a top-down recessing of the BARC.

The present disclosure further provides a method of manufacturing anintegrated circuit device. In the method, a semiconductor substrate isreceived, and one or more layers are formed on the semiconductorsubstrate. The one or more layers establish a topographically variableupper surface which includes a plurality of regions having differentvertical heights from one another and being spaced horizontally apartfrom one another. A bottom anti-reflective coating (BARC) is providedover the topographically variable upper surface and extends downwardlybetween sidewalls of the plurality of regions. Chemical mechanicalpolishing (CMP) is carried out to planarize an upper surface of theBARC; and a top-down recessing of the planarized upper surface of BARCis performed.

The present disclosure further provides a method of manufacturing anintegrated circuit device. In the method, a semiconductor substrate isprovided. One or more layers are formed on the semiconductor substrate.The one or more layers establish a topographically variable uppersurface which includes a plurality of regions having different verticalheights from one another and being spaced horizontally apart from oneanother.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of manufacturing an integrated circuitdevice, the method comprising: processing a semiconductor substratethrough a series of operations to form a topographically variablesurface over the semiconductor substrate, wherein the topographicallyvariable surface varies in height across the semiconductor substrate;providing a polymeric bottom anti-reflective coating (BARC) over thetopographically variable surface; performing chemical mechanicalpolishing (CMP) to remove a first portion of the BARC; and etching toeffectuate a top-down recessing of the BARC.
 2. The method of claim 1,wherein providing the BARC is carried out by spin coating.
 3. The methodof claim 1, further comprising: after the BARC is provided over thetopographically variable surface and before performing CMP, inducingcross-linking in the BARC by baking.
 4. The method of claim 1, whereinthe etching to effectuate the top-down recessing of the BARC removes anupper portion of the BARC while leaving a lower portion of the BARC inplace.
 5. The method of claim 1, wherein the etching to effectuate thetop-down recessing of the BARC results in a planar upper BARC surface.6. The method of claim 5, wherein the planar upper BARC surface isco-planar with an upper surface of a layer included in thetopographically variable surface.
 7. The method of claim 1, whereinprior to the etching, the BARC extends over an uppermost surface of alayer included in the topographically variable surface; and whereinafter the etching, a recessed upper surface of the BARC has beenrecessed to a height that is less than that of the uppermost surface ofthe layer, such that the uppermost surface of the layer protrudes abovethe upper surface of the BARC.
 8. The method of claim 1, wherein thetopographically variable surface includes a first layer extendingupwardly over the semiconductor substrate and a second layer extendingupwardly from over an upper surface of the first layer, the BARC beingprovided to extend over both the first and second layers; wherein theetching recesses an upper surface of the BARC such that the recessedupper surface of the BARC is co-planar with the upper surface of thefirst layer.
 9. The method of claim 8, wherein the etching removesportions of the second layer above the upper surface of the BARC. 10.The method of claim 8, wherein the etching leaves the second layerintact such that a portion of the second layer protrudes upwardly beyondthe recessed upper surface of the BARC.
 11. The method of claim 8,wherein the first layer or the second layer is a hard mask.
 12. Themethod of claim 8, wherein the first layer or the second layer is a workfunction metal that forms part of a metal gate electrode.
 13. The methodof claim 1, wherein the etching to effectuate the top-down recessing ofthe BARC completely removes the BARC.
 14. A method of manufacturing anintegrated circuit device, the method comprising: receiving asemiconductor substrate; forming one or more layers on the semiconductorsubstrate, the one or more layers establishing a topographicallyvariable upper surface which includes a plurality of regions havingdifferent vertical heights from one another and being spacedhorizontally apart from one another; providing a bottom anti-reflectivecoating (BARC) over the topographically variable upper surface, the BARCextending downwardly between sidewalls of the plurality of regions;performing chemical mechanical polishing (CMP) to planarize an uppersurface of the BARC; and performing a top-down recessing of theplanarized upper surface of BARC.
 15. The method of claim 14, whereinthe chemical mechanical polishing stops above an uppermost surface ofthe one or more layers and leaves an amount of the BARC in place abovethe uppermost surface.
 16. The method of claim 14, further comprising:after the BARC is provided over the topographically variable uppersurface and before performing CMP, inducing cross-linking in the BARC bybaking.
 17. The method of claim 14, wherein performing the top-downrecessing of the planarized upper surface of BARC removes an upperportion of the BARC while leaving a lower portion of the BARC in placeimmediately after the top-down recessing.
 18. The method of claim 14,wherein etching to effectuate the top-down recessing of the BARC resultsin a recessed planar upper BARC surface.
 19. The method of claim 18,wherein the recessed planar upper BARC surface is co-planar with anupper surface of a layer included in the topographically variablesurface.
 20. A method of manufacturing an integrated circuit device, themethod comprising: receiving a semiconductor substrate; forming one ormore layers on the semiconductor substrate, the one or more layersestablishing a topographically variable upper surface which includes aplurality of regions having different vertical heights from one anotherand being spaced horizontally apart from one another.